The following description of the background of the invention is provided simply as an aid in understanding the invention and is not admitted to describe or constitute prior art to the invention.
There are five major fat-soluble vitamins or vitamin related substances in humans: vitamins A, K, D, and E, and carotene. Vitamin A (retinol) is the immediate precursor of two important biologically active metabolites: retinal (needed for scotopic and color vision), and retinoic acid (a hormone-like growth factor for epithelial and other cells). Thus retinol is associated with the function of vision, epithelial cell integrity, bone remodeling, and reproduction. Vitamin E exists in eight different forms (isomers): alpha (α), beta (β), gamma (γ), and delta (δ)-tocopherol; and alpha (α), beta (β), gamma (γ), and delta (δ) tocotrienol. Alpha-tocopherol is the most active form of vitamin E in humans, and may be an important lipid-soluble antioxidant in the protection of cell membranes from oxidation from radicals produced in the oxidation of fats. Alpha-tocopherol is the most studied of the vitamin E isomers, with all other forms much less studied.
Various methods have been reported in the art for measuring vitamin A, α-tocopherol, β-tocopherol and γ-tocopherol, either individually or in various combinations. For reports of detection of vitamin A, see e.g., Deuker, S., et al., Anal. Chem. 1994, 66:4177-85 (reporting quantitation of derivatized retinol by gas chromatography-mass spectrometry); Wang, Y., et al., J. Mass Spectrom. 2001, 36:882-88 (reporting quantitation of vitamin A (retinol) in rat prostate with liquid chromatography-mass spectrometry); Li H., et al., et al., J. Chromatog. B 2005, 816:49-56 (reporting quantitation of all-trans-retinol in fish eggs by liquid chromatography-tandem mass spectrometry with positive electrospray ionization); Rühl, R., Rapid Commun. Mass Spectrom. 2006, 20:2497-2504 (reporting quantitation of retinol in serum and cell extracts by liquid chromatography-diode-array detection atmospheric pressure chemical ionization tandem mass spectrometry). For reports of detection of α-tocopherol and/or γ-tocopherol, see e.g., Walton, T., et al., Biomed. Environ Mass Spectrom. 1988, 16:289-98 (reporting fragmentation spectra of α and γ forms of tocopherol generated by tandem mass spectrometry of pure samples); Lauridsen, C., et al., Anal. Biochem. 2001, 289:89-95 (reporting quantitation of α-tocopherol in plasma by HPLC-tandem mass spectrometry); Mottier, P., et al., Anal. Biochem. 2002, 301:128-135 (reporting quantitation of α-tocopherol in plasma by GC-tandem mass spectrometry and HPLC-tandem mass spectrometry); Hao, Z., et al., J. Chromatog. A 2005, 1094:83-90 (reporting quantitation of α-tocopherol in botanical materials by liquid chromatography-tandem mass spectrometry); Stöggl, W., et al., J. Sep. Sci. 2005, 28:1712-18 (reporting reverse phase liquid chromatographic separation of α-tocopherol and γ-tocopherol with a C-30 chromatography column); and Nagy, K., et al., Anal. Chem. 2007, 79:7087-96 (reporting quantitation α-tocopherol and γ-tocopherol in plasma with normal phase liquid chromatography-tandem mass spectrometry). For reports of detection of two or more of vitamin A, α-tocopherol, and γ-tocopherol, see e.g., Khachik, F., et al., Anal. Chem. 1992, 64:2111-22 (reporting detection of vitamin A, α-tocopherol, and γ-tocopherol from extracts of human plasma with HPLC); Khachik, F., et al., Anal. Chem. 1997, 69:1873-81 (reporting quantitation of vitamin A, α-tocopherol, and γ-tocopherol in serum and breast milk with high performance liquid chromatography—photodiode array detection—mass spectrometry); Heudi, O., et al., J. Chromatog. A 2004, 1022:115-23 (reporting simultaneous quantitation of vitamin A and E (form unspecified) in infant formulae by liquid chromatography-mass spectrometry); Andreoli, R., et al., Anal. Bioanal. Chem. 2004, 378:987-94 (reporting simultaneous determination of vitamins A (retinol) and α-tocopherol in serum with liquid chromatography-tandem mass spectrometry); Capote, F., et al., Rapid Commun. Mass Spectrom. 2007, 21:1745-54 (reporting quatitation of liposoluble vitamins including vitamin A (all-trans-retinol) and α-tocopherol in human serum with liquid chromatography-triple quadrupole tandem mass spectrometry); and Kamao, M., et al., J. Chromatog. B 2004, 1022:115-23 (reporting quantitation of fat soluble vitamins (including vitamins A (retinol) and α-tocopherol) in breast milk by liquid chromatography-tandem mass spectrometry).